The need to conserve water in many parts of the world to support increasing demands placed on water resources by growing populations competing with environmental requirements is becoming more evident with time. This has fuelled interest in ways to minimize evaporative losses from open storages.
Numerous suggestions to minimize evaporation involving the use of floating objects have been made in the past with different degrees of success and associated problems. While evaporative loss is known to be reduced by covering the surface of the water with a cover of plastic or like sheeting, and while such techniques are used with success in swimming pools, such arrangements have limited success with water storage facilities having large surface areas which are exposed to extreme weather conditions, and particularly high winds.
Other suggestions include the use of floating balls and other floating covers made from plastic sheeting. In a study conducted by one of the present inventors, floating water surface modules which cover most of the surface of the water have been determined to provide a practical solution for large water surface areas, as they are relatively stable in high winds.
A cover which may be used in the above way is disclosed in WO 98/12392, which shows a floating cover molded from a suitable plastic and having vertical sides and a domed cover, buoyancy being provided by a compartment extending across the corner between the sides and the cover. While the arrangement described may be capable, with some modification, of mass production, it has the disadvantage of not being able to be arranged in a stable stack for storage or distribution, thereby increasing storage and distribution costs when required in the quantities necessary to cover a large body of water, and rendering it less suitable as a mass production candidate.